The method relates to a diagnostic method for electrical devices, in particular automobile radio devices.
Some conventional automobile radio devices have a testing, adjustment and starting interface apparatus are known. This very fast bus interface allows, both during the production process and for service purposes, fast and standardized test sequences which can be performed under computer control. For this purpose, minimal software which supports these tests is integrated into the devices in a memory. This software, which is generally stored in RAM, can load and start a test program which is connected from the outside to the interface. All that is necessary for this is a short program routine. Once the test is complete, the result is reported back via the interface. In this context, the test times should be kept as short as possible, which is achieved by appropriate design of the data bus between the control computer and the device to be tested.
Some conventional automobile radio devices also have a reading device for the introduction of a chip card. The chip card contains a security code. Operation of the automobile radio is possible only if the security code via the chip card agrees with the code stored in the automobile radio.
The diagnostic method according to the present invention has the advantage, in contrast, that diagnosis of the functions of the device is possible without having to remove the device from the vehicle. In addition, troubleshooting is also possible utilizing the device environment directly in the installed state. Diagnosis is thus expanded to encompass real operating conditions, e.g. including all connected components. The diagnostic method takes place directly on the device: no wiring or soldering of connecting wires is necessary, and it is also not necessary to connect a computer or tester.
It is particularly advantageous that the results of the diagnosis are written back onto the chip card which contains the test software.
It is furthermore advantageous that the results can also be output directly to the device""s display.
For many test instances it is necessary to load larger test programs into the device, so that the storage capabilities of a single chip card are not sufficient. With our method according to the present invention, however, it is easily possible to distribute the test software among several chip cards and read them successively into the device.